1. Field of the Invention
The present invention relates to a free-flow conveyer chain installed in an assembling line of a light-weight product such as an electronic component and the like.
2. Description of the Prior Art
In a conveyer installed in the assembling line of the light-weight product such as the electronic component and the like, it is often necessary to temporarily keep the product stationary in a certain step on the midway of the line. However, even when such necessity occurs in a certain step, products residing in other steps often must be moved in the same assembling line. Namely, it is necessary for the conveyer installed in the assembling line to permit some products to be free from the motion of the conveyer, while the conveyer permits the flow of the other products.
Consequently, for example, as shown in FIG. 5, in a conventional free-flow conveyer chain installed in the assembling line, a pin 1 is shaped into an elongated form larger in length than the width of a chain element 2 while inserted at its opposite ends into a pair of supporting rollers 4 for supporting an article 3 being transmitted, so that the pair of supporting rollers 4 are rotatably engaged with the pin 1. After being inserted into the supporting rollers 4, the pin 1 is press-fitted at its opposite ends to a pair of washers 5 each of which serves as a stopper means for preventing each of the supporting rollers 4 from dropping out of the pin 1, whereby the supporting rollers 4 are permitted to pass through a bottom surface 3a of the article 3 while rotatably driven. Incidentally, the reference numeral 6 denotes a guide rail for guiding the free-flow conveyer chain along the assembling line.
In such conventional free-flow conveyer chain, however, since the supporting rollers 4 are provided rotatably, it is impossible for such supporting rollers 4 to exert any traction on the article 3 being transmitted. As a result, at a time when the conveyer chain begins its operation or changes its operation speed, the article 3 to be transmitted by the conveyer chain begins moving under the influence of its inertia independently of the motion of the conveyer chain to cause a disturbance of article flow in which the articles 3 ar equally spaced from each other.
Further, in a conventional speed-amplifying free-flow conveyer chain, in order to make the transmitting speed of the article 3 larger than the traveling speed of the conveyer chain, the supporting roller 4 is rotatably driven by a small-diameter roller connected thereto, which small-diameter roller is smaller in diameter than the supporting roller 4 and supported by a guide rail 6 so as to be rotatably driven thereby when moved therealong. Namely, the supporting roller 4 is press-fitted to an extended boss of the small-diameter roller, so that the supporting roller 4 is rotatably driven with an unecessarily large and constant torque to cause a disturbance of the positioning of the article 3 and a collision of the articles 3 at a time when some article 3 is temporarily kept stationary in its transmitting operation, which causes a large energy loss.
In order to resolve the above problem, hitherto, as shown in FIG. 5, a spring 7 is interposed between one of the supporting rollers 4' and a washer 5 to produce a frictional force between the supporting roller 4' and an outer link plate 8 so as to impart a braking torque to the supporting roller 4'. A plurality of the thus constructed supporting rollers 4' are distributed to adequate positions over the conveyer chain so as to balance the inertia of the article 3 being transmitted, in order to accommodate the article 3 to the operation of the conveyer chain at a time when the conveyer chain begins to move or changes its operation speed.
Incidentally, although the thus constructed supporting rollers 4 for producing the braking torques are distributed to the adequate positions over the conveyer chain, they are adjusted in number and spacing so as to be accommodated to the actual assembling line through trial operations of the conveyer chain in site.
However, in the conventional conveyer chain employing the spring 7 as a means for imparting the braking force to the supporting roller 4', since the spring 7 requires its compression space, it is impossible for the supporting roller 4' engaged with the spring 7 to have a boss portion 4a at its outer side portion in contrast with a normal supporting roller 4 shown in a left-hand side of FIG. 5. Consequently, it is necessary for the conventional conveyer chain to provide both types of the supporting rollers 4 and 4', which increases the number of the parts of the conveyer chain to cause the part control and the assembling work of the parts to be troublesome, and also cause the adjusting work of the conveyer chain in site to be troublesome, so that much manual work is required to lead to a large labor and cost. In addition, since the spring 7 varies in quality according to variations of material, heating-treatment conditions, filament diameter, coil diameter and pitch, it is necessary to purchase at a time a large number of the springs 7 produced in the same lot, in order to accomplish the quality control of the springs 7. These are problems inherent in the conventional conveyer chain.